Process of producing pure magnesium



June 6, 1939. F. HANSGIRG,

PROCESS OF PRODUCING PADRE MAGNESIUM June 6, 1939. F. HANSGIRG 2,150,969

PROCESS OF PRODUCING PURE MAGNESIUM .Original Filed Feb. 5, 1933 5 Sheets-She-et 2 Ld INYENT OR.

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UNITED STATE Patented June 6, 1939 PROCESS F PRODUCIN G PURE MAGNESIUM Fritz Hansgirg, Radenthein, Austria, assignor to American Magnesium Metals Corporation,

Pittsburgh, Pa., a corporation of Delaware Original application February 3, 1933, Serial No.

655,067. Divided and this application November 20, 1934, Serial No. 753,890

'I'his invention relates to a process of producing substantially pure magnesium.

Like all solid substances having a considerable vapor tension even below their melting point,

metallic magnesium displays a tendency to pass directly from the condition of vapor into the solid state, without the occurrence -of ,a liquid phase. It has therefore been repeatedly recommended to purify magnesium by sublimation or to produce it in crystalline form, from magnesium-containing starting materials, a process which, however, is attended inter alia, with the drawback, in operating on a technical scale, that it can only be performed in a periodic manner. 0n the l5 other hand, the distillation of magnesium has hitherto encountered serious dilculties.

One object of the present invention is to separate substantially pure magnesium from nonvolatile concomitant substances.

Another object lof my invention is to enable magnesium to be distilled so as to condense the distillate as a liquid deposit.

A further object of the invention is to provide a process for the distillation of material containing metallic magnesium which can be carried on continuously.

My process comprises passing crude metallic magnesium, or material high in magnesium, continuously through a heated zone, in order to heat it to a temperature above the melting point, and

preferably in the neighborhood of the boiling point of magnesium, the disengaged vapors being carried by an inert or reducing gas, through an interposed filter, into the condensing zone, the

vapors being prevented from cooling below the solidication point of the magnesium, by being heated on their way to the condensing zone, and

being thereafter suddenly cooled to the condensation point. The filtration serves to remove con- -vapors. This process is performed at reduced pressures.

While various types of apparatus might be employed for carrying out this process, a typical ap- 45 paratus according to the present invention consists substantially of an externally heated distillation chamber which is provided with a conveyor and connected, at each. end, with lock chambers, through a stock vessel or collector, and 50 also with a condenser from which the molten magnesium runs oil.' into a collector, rfor example, through a barometric outlet, a illter being interposed between the said distillation chamber and the said condenser. The still, filter, condenser, 56 outlet and receiver are preferably housed in a taminating particles of dust from the metallic (c1. {x5-67) A common heating chamber, such as an electric radiation furnace.

In order to render the filtration process continuous, it is advisable to employ a filter of loose, granular material, piled up loosely between an in- 5 take and closable outlet, in' the passage connecting the still chamber with the condenser.

In a preferred embodiment of apparatus for carrying dlt the invention, the condenser consists of a hollow body, closed below and internally 10 cooled, and preferably with a curved bottom,- said body being disposed in.a heated jacket in such a y manner that the incoming vapors bathe the lowest portion of the cooling surface. This cooling tube is preferably provided with a device for 15 maintaining a liquid orgaseous cooling medium in circulation therein, the arrangement being such that the heat is transmitted through the outer tube tothe cooling medium principally by radiation. To enable the cooling action to be accu- 20 rately regulated, it is advisablev to arrange said circulating device so as to be vertically adjustable. A

In order more clearly to understand the nature of the invention, reference is made to the accom- 25 panying drawings, which illustrate diagrammatically and by way of example, an embodiment of apparatus suitable for carrying out the process of the invention.

In said drawings Fig. 1 shows a front elevation 30 in partial section; Fig. 2 a cross section; Fig. 3r a vertical section through 'a modied embodiment; and Fig. 4 a detail of a further modiiication.

Like reference characters denote like parts in' 35 the several flgures .of the drawings. According tothe embodiment shown in Figs. 1

and 2, the distillation chamber l is in the form of a tube which extends through a suitable heating apparatus, such as an electric radiation fur- 40 nace 2. 'Ihe material to be distilled is placed in a charging hopper 3 and passes through a lock chamber 4 having closure members 5 and 6 oper.- able by levers, as shown, into a stock vessel 1, f from which it is continuously fed, by means of a worm 8 or the like, into vdistillation chamber I, through which the material is conveyed by means of a. worm 9 or the like. Theresidue falls into a collector I0, from which it is discharged through 'a lock chamber II provided with closure mem- 50 vbers 5a and 8a. 'I'he collector I0 and -chamber Il,`as also the chamber 4 and stock vessel 1, are connected with a vacuum pump by means of pipes, as shown in Fig. 1, adapted to be closed independently. I5

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Midway along its length the distillation tube Il is connected by a conduit I2 with the outer shell I3 of a condenser, the discharge pipe |43 of which receiver which may be used in connectionwith the present process, and which is similar to that shown in Ullmann Enzyklopaedie der Technischen Chemie of 1929, second edition, third' volume, at page 610. It comprises two receivers 65, 65a which may be connected alternatively by means of the three-way valve i6 through pipe lil to the condenser. Each of the receivers is adapted to be connected with the vacuum pump or the atmosphere by means of pipes controlled by valves 638, lita, and 69, 69a, respectively. The discharge pipes of the receivers "l5 and lia may be closed independently byvalves 53 and 53a, respectively. Before the distillate is allowed to ow through the pipe It and the valve i6 to the receiver (l5, the valve i8 will be opened to provide a vacuum and the valves i9 and 53 will be closed. Simultaneously the distillate may be discharged from the receiver Ila.; for this purpose, after closing the valve d8a and opening the valve (59a the valve 53a is opened. When the receiver t'a is to receive the distillate and the receiver l5 is to be discharged the operation of the. valves is reversed.

As shown in Fig. 2, the condenser consists of a cylindrical hollow vessel' Il, closed below by a curved bottom and disposed upright in a heated shell I3, in such a manner that the incoming vapors bathe the lowest portion of the cooling surface. A tube I8 is centered in the tube I'i so as to leave a small intermediate space all round and allow the transmission of heat to take place principally by radiation, and tube I8 is cooled by means ofa liquid or gaseous cooling medium, which is admitted through the tube Illa and passes away through the lateral branch I9b. The Whole of the circulation device is vertically adjustable in the tube Il, in order to enable the cooling action to be accurately regulated.

In order to remove accompanying dust, a iilter' is interposed in the pipe I2 connecting the chamber I with the condenser I3. The ltering medium consists preferably of loose, granular material, such as sintered magnesite or coal slack, disposed loosely in the connecting pipe. The arrangement shown in Fig. 2 has been adopted to enable the filtering medium to be replenished without interrupting the work. The ltering medium 2li is disposed in a hopper 2l, to the lower .end of which is attached a tube 23, which can be closed by a valve 22 and dips into a collector 2Q, Whilst a pipe 25, leading from a stock vessel 26, rests on the heap. On the valve 22 being opened, the entire column of material is set in motion, the

active portion becoming changed. If desired,v

the valve can be left slightly open all the time, so that the changing is continuous. Since the ltering mediu'mis more rapidly clogged up on the intake side than on the discharge side, it is advisable to arrange that the changingv of the medium does not proceed with the same velocity on the two sides. For this purpose a deltoid member 2l is disposed, slightly eccentrically, in the hopper 2 I, so that the outlet passage on the intake side of the vapors is wider than the passage on the outlet side, and the medium accordingly moves more rapidly on the intake side than at the outlet side.

In order to direct the flow'of the magnesium vapors, they are conducted to the condenser by means of a current of inert orreducing gas, such as hydrogen. For this purpose, supply pipes 28, 29, Ell),A 3| are employed, which, in the example shown, are attached at both ends of the reaction chamber I (Fig. 1) and to the stock vessel 26 and outlet pipe 23 (Fig. 2), respectively.

The material to be distilled, such as magnesium dust furnished by the electrothermal reduction of magnesium compounds, is heated in the heating zone to a temperature-according to the degree of vacuum-at which the magnesium already possesses a high vapor tension, preferably to a temperature near (slightly above) the boiling point. The pipe I2 leading to the condenser (Fig. 1), the lter and the shell I3 of the condenser are heated to such an extent that the internal temperature can not fall below the solidiiication temperature of the magnesium. If the distillation be conducted within a pressure range of 50 to 200 mm. mercury gauge, the distillation tube and the other heated members of the device are maintained at a temperature between 850 and 100ll C. The actual cooling temperature of the condenser is between 680 and 800- C.

According to the embodiment shown in Fig. 3, the horizontal reaction chamber is replaced by a vertical tube 32, forming the casing of one side of a bucket elevator 33. Before entering the heated portion of the casing 32, the buckets 3G are filled with magnesium-containing material from a stock vessel 35 and this material is thereafter covered by filtering material discharged from a stock vessel 3l. The outletsof each vessel are adapted to be closed by slides @6, 38, respectively. The vapors generated in the heated section of the tube 32 pass through the' iiltering medium and are carried o to the condenser It by means of the flushing gas admitted at 39 and 10.

Instead of conveying the material to be distilled through the distillation zone by means of a worm or bucket elevator, the process can also be carried out with the aid of other suitable known devices permitting the flow of the material under the iniuence of gravity (such as for instance stationary furnaces Acomprising a series of hearths in step relation), or by rotation of a heated tube round its long axis (such as revolving furnaces), or by stationary furnaces provided with paddleshaped conveying devices. It is only essential that the magnesium-containing material pass through'a heated zone so as to be brought to a temperature which causes transformation of the magnesium into the state of vapor, which temperature, of course, depends on the pressure conditions eiristing in the heated system, and that, j

from nickel and copper, must be employed for constructing the apparatus of the present invention in order to prevent contamination of the resulting magnesium.

This application is a division of my copending 4application .seran No. 655,067, mea February a,

According to the provisions of the patent statutes, I have explained the principle and mode of operating my invention, and have illustrated and described what I now consider to be its best embodiment. However,'I desire to have it understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specically illustrated and described.

I claim:

A method of treating magnesium powder which comprises subjecting said powder to a temperature above the melting point, maintaining said powder in a continuous state .of Aagitation to subject the same toa rubbing action.V the temperature and pressure being such as to cause vaporization of magnesium, rernoving the vapors and condensing the same.

FRITZ HAN SGIRG. 

